This mysterious man, known only as Bastion, saw himself as humanity's last "bastion" of defense against the evil mutants. But though he himself did not know it at first, the man who called himself Bastion was actually a Sentinel in disguise as a human. He started out as Master Mold (featured in X-Men III: The Official Video Game), an immense Sentinel designed by Bolivar Trask. After Master Mold was destroyed by Banshee, one of Nimrod's opponents, Master Mold mixed with and reconstructed Nimrod, and infiltrated by the Master Mold's system.

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